Background. Obese women are 80 times more likely to develop Type 2 diabetes than those who maintain a lean weight. Intergenerational obesity is common, with maternal obesity a strong risk factor for the development of overweight in young children. The Diabetes Prevention Program (DPP) identified strategies for achieving weight loss through lifestyle change, but translation to real world settings remains challenging. Aims. This study will test Healthy Eating & Active Living Taught at Home (HEALTH), which adapts and integrates the DPP lifestyle intervention within Parents As Teachers (PAT), a national home visiting program. HEALTH will be delivered by parent educators to obese mothers of overweight/obese preschoolers through 36 home visits, 24 group meetings, and 18 booster telephone calls. Our primary hypothesis is that participants in HEALTH will achieve a 7% weight loss at 12 months and maintain a 5% weight loss at 24 months, which will be at least two-fold greater than that achieved in the usual care control group. Secondary aims will determine whether improvements in 'mother to child' behaviors of HEALTH participants will explain all or part of changes in the weight trajectory of the participant's overweight/obese preschool child. An extensive program evaluation will address elements of external validity. Methods and Evaluation. A two group randomized nested cohort design with data collected at baseline, 12, and 24 months, will evaluate weight, clinical, and behavioral outcomes of participants randomized to either control sites (N=8 sites; 128 participants) receiving the standard PAT program or intervention sites (N=8 sites; 128 participants) receiving HEALTH. Evaluation will include elements of reach and representativeness, implementation and adaptation, decision making outcomes, maintenance and institutionalization, and cost. Innovation. This proposal will overcome translational barriers and optimize the fit between evidence-based practice and the practice context. HEALTH has the potential for dissemination across all 50 states to 2200 PAT sites and 9600 educators reaching approximately 58,000 obese mothers and children.